Some local area networks (LANs) use more than one wide area network (WAN) from different Internet Service Providers (ISPs) for access to the Internet. Typically, each terminal device within the LAN is assigned with multiple IP addresses corresponding to the multiple ISPs, which may be static or dynamic IP addresses. To balance the traffic, the multiple WANs can be assigned to different user groups of the LAN. Alternatively, the WANs can be assigned based on the target IP addresses. Either type of assignment with respect to the usage of the WANs is usually defined by an LAN user and remains fixed until being manually changed.
In real life, with regard to a certain target IP address, a different WAN coupled to the LAN may sometimes offer better service quality than the assigned WAN. However, limited by the fixed WAN assignment, the LAN cannot make efficient use of the services provided by the multiple ISPs.